[CALCITE-7353] introduce Milvus adapter with scan and convention support

[wg1026688210]

Add the foundational Milvus adapter module to Apache Calcite:

• MilvusRel convention interface and MilvusTableScan operator
• MilvusSchema / MilvusSchemaFactory for schema integration
• MilvusTranslatableTable with scan() for collection reads
• MilvusToEnumerableConverter and converter rule for code generation
• MilvusQueryEnumerator with pagination via MilvusRowIterator
• MilvusProjectExpression for projection handling
• Test infrastructure: E2E base, JUnit 5 extension, Testcontainers

This is the minimal skeleton; Filter/Project/VectorSearch rules are intentionally omitted for subsequent PRs.

[cjj2010]

CI error:
"Caused by: java.lang.IllegalStateException: Could not find a valid Docker environment. Please see logs and check configuration"
It seems to be related to the Docker environment. Alternatively, you can check how the Redis adapter builds the Docker environment

[sonarqubecloud]

Quality Gate passed

Issues
16 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wg1026688210]

@cjj2010 @xuzifu666 @mihaibudiu cc ,the pr is ready

[mihaibudiu]

I was expecting to see some kind of README for such a large project, explaining what Milvus is, how it relates to Calcite, and how people can use the adapter. Or perhaps there's some other place for the adapters documentation? But I don't see any.

[xuzifu666]

I was expecting to see some kind of README for such a large project, explaining what Milvus is, how it relates to Calcite, and how people can use the adapter. Or perhaps there's some other place for the adapters documentation? But I don't see any.

Thank you for the contribution @wg1026688210 ! As @mihaibudiu mentioned, we can first add some background and value information in Jira. Currently, we support many adapters, and the universality and uniqueness of adapters are important reference indicators for introducing adapters.

[wg1026688210]

I was expecting to see some kind of README for such a large project, explaining what Milvus is, how it relates to Calcite, and how people can use the adapter. Or perhaps there's some other place for the adapters documentation? But I don't see any.

Thank you for the contribution @wg1026688210 ! As @mihaibudiu mentioned, we can first add some background and value information in Jira. Currently, we support many adapters, and the universality and uniqueness of adapters are important reference indicators for introducing adapters.
Hi~ @xuzifu666 @mihaibudiu Thanks for your feedback. There have been some discussions in this Jira.

[xiedeyantu]

Thank you for the contribution @wg1026688210 ! Although I don't know much about Milvus, I think this adapter is very valuable. As @zabetak stated in CALCITE-6908, the test coverage of the milvus adaptor should ideally reach 80%. I suggest including test cases along with the feature descriptions and adding the test cases mentioned in the descriptions to the code. This will make it easier for reviewers to review the code.